How to... upgrade your car's stereo - Audi A8: bangs for your buck

The finest stereo we've tested to date is the Bang & Olufsen Advanced Sound System, optional on Audi's A8. Offering a staggering 1000 watts of power, it uses 14 individually amplified loudspeakers. This is technology similar to that used in Bang & Olufsen's £10,000 BeoLab 5 speakers in our picture.

The A8's real party trick, though, are high-frequency (treble) speakers that rise, electronically, from protective housings in the dashboard. These 'tweeters' are key to the system's sonic ability, giving it tonal purity and stereo imaging unrivalled by any car system we've heard. There's only one snag - it costs £4500...